A recent study evaluated the frequency and characteristics that predicted coinfection of M genitalium and chlamydia in women and the frequency of M genitalium with macrolide resistance-associated mutations after chlamydia treatment with azithromycin.

According to a study published in Sexually Transmitted Diseases, although coinfection with Mycoplasma genitalium among women with chlamydia occurs infrequently, this may be population-dependent. The researchers also noted that a significant number of women who took part in the study had repeat M genitalium detection at follow-up, likely because of macrolide resistance-associated mutations that resulted in a nonresponse to azithromycin prescribed for chlamydia.

The sexually transmitted M genitalium infection is associated with pelvic inflammatory disease, cervicitis, and infertility in women, and the reported prevalence of M genitalium detection in women with chlamydia ranges from 4.8% to 42.9% in available studies — none of which evaluate M genitalium outcomes for women treated for chlamydia and M genitalium coinfection with azithromycin. The first-line treatments for chlamydia — azithromycin and doxycycline — both have low cure rates against M genitalium. The current study was designed to investigate the frequency and characteristics that predicted coinfection in women (N=302), and the frequency of M genitalium with macrolide resistance-associated mutations leading to repeat detection at 3-month follow-up after chlamydia treatment with azithromycin.

The 302 women with chlamydia who took part in the study ranged between the age of 16 and 50 (median age 22 years). Of this number, 93% were black, 42.1% were on hormonal contraception, 48.7% had a prior chlamydia infection (by medical record or self-report), 52.3% had no urogenital symptoms, 28.8% had bacterial vaginosis, 2.7% had pelvic inflammatory disease, 12.6% had vulvovaginal candidiasis, 18.9% had cervicitis, 3.6% had Trichomonas vaginalis infection, and 7.3% (n=22) had M genitalium. None of these characteristics among participants, including the presence or absence of symptoms, showed significant associations with M genitalium coinfection.

Of the 21 patients who returned for a 3-month follow-up visit, 28.6% (n=6) had M genitalium detected, and all 6 of these had M genitalium strains with a macrolide resistance-associated mutation. Although 83.3% (n=5) of these 6 participants also had a M genitalium strain with an macrolide resistance-associated mutations detected at baseline, one participant (16.7%) had a wild-type strain, indicating that treatment with azithromycin may have contributed to macrolide resistance-associated mutation development.

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The study was limited by a small sample size. The study investigators concluded that “our study demonstrated that [M genitalium] coinfection occurred infrequently in our cohort of [Chlamydia trachomatis–infected] women; however, when considering findings from other published studies, it appears prevalence of [M genitalium] co-infection in [C trachomatis–infected] women may depend on the population that is being investigated.”